Magnum heads...what spark plug?

First question: Do the magnum plugs have 2 different reaches? 1/2" and 3/4"?
Projection tip or no??

I'm looking for a plug for an early 340 with EQ aftermarket heads, most likely a couple of heat ranges colder than the stock 340 application, but will start with the OE heat range first if needed.

Your input is appreciated!